The increased BP results in arterial fibrinoid necrosis. Endothelial damage leads to activation of the clotting cascade and release of vasoconstrictor substances.
The RAS system and catecholamine release are triggered.
Pre-existing HTN actually lowers probability of hypertensive emergency through adaptive methanisms.
You also get increased release of cytokines due to mechanical stretching of vessel

Describe Autoregulation

A protective mechanism by which cerebral blood flow maintains a constant cerebral perfusion over a large range of MAP. Chronically hypertensive patients have a right shift in the autoregulatory curve, so that cerebral blood flow is not maintained at low MAP avlues compared to non-hypertensives. Hypertensives require higher MAP to maintain adequate cerebral blood flow.

TREAT THE PATIENT, NOT THE BP READING
-To lower BP or DBP over an ceeptable time frame based on severity of the crisis and individual tolerance without provoking cerebral or cardiac hypoperfusion, stroke or MI

Describe Goals of therapy for Hypertensive Emergency

Decrease MAP by 20-30% over 30-60 minutes or decrease DBP by 5-10mmHg q 5-10 min to a diastolic pressure of 100